Special Issue "Synthesis and Properties of Bulk Nanostructured Metallic Materials"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 December 2017)

Special Issue Editor

Guest Editor
Prof. Dr. Byungmin Ahn

Department of Materials Science and Engineering & Energy Systems Research, Ajou University, Suwon 443-749, South Korea
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Special Issue Information

Dear Colleagues,

Bulk nanostructured materials (BNMs) are defined as polycrystalline bulk solids with nanocrystalline (NC) or ultrafine-grained (UFG) microstructures. These BNMs have received increasing attention because of the potential of their improved properties and promising applications compared to conventional coarse-grained materials with the same chemical compositions. For example, BNMs exhibit superior mechanical properties, such as strength or hardness, unachievable with conventional counterparts. This is generally attributed to a large portion of the volume being associated with disordered grain boundary regions because of the extremely fine grain sizes of BNMs. Recent advances in the synthesis and processing techniques of BNMs drive our need to understand the underlying fundamental phenomena as well as their significant properties. Research on the synthesis and properties of BNMs is one of the most emerging fields in advanced structural materials systems. This Special Issue covers a wide scope in the research field of BNMs, and we cordially invite original research articles and reviews of the recent achievements on the following subjects of BNMs:

  • Synthesis and processing techniques
  • Development of novel experimental methods
  • Advances in severe plastic deformation (SPD) processing and SPD materials
  • Powder processing and powder metallurgy materials
  • Deformation mechanisms and experimental mechanics
  • Mechanical and physical properties
  • Microstructural evolution and characterization
  • Computational and analytical modeling
  • Structural, functional, and biomedical applications

Prof. Dr. Byungmin Ahn
Guest Editor

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Keywords

  • Bulk nanostructured materials
  • Nanocrystalline materials
  • Ultrafine-grained materials
  • Severe plastic deformation
  • Grain refinement
  • Mechanical properties
  • Microstructure

Published Papers (11 papers)

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Research

Open AccessArticle Template-Assisted Fabrication of Nanostructured Tin (β-Sn) Arrays for Bulk Microelectronic Packaging Devices
Metals 2018, 8(5), 347; https://doi.org/10.3390/met8050347
Received: 23 March 2018 / Revised: 8 May 2018 / Accepted: 8 May 2018 / Published: 11 May 2018
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Abstract
In this study, uniform and ordered nanostructured arrays of pure tin (Sn) were produced by the chemical pulse plating method in potentiostatic mode. Bottom metalized anodic aluminium oxide templates were used as the substrates for holding nanostructures during deposition. The plating bath consists
[...] Read more.
In this study, uniform and ordered nanostructured arrays of pure tin (Sn) were produced by the chemical pulse plating method in potentiostatic mode. Bottom metalized anodic aluminium oxide templates were used as the substrates for holding nanostructures during deposition. The plating bath consists of stannous sulfate (SnSO4), sulfuric acid (H2SO4), polyethylene glycol (PEG), and glutaraldehyde as a surfactant. The effect of potentiostatic potential ranging from −0.5 to −3.2 V vs. Ag/AgCl electrode was studied on the growth morphology of nanostructures that were formed. The characterization studies were accomplished by X-ray diffraction (XRD), field emission electron microscopy, and energy dispersive spectroscopy. It was found that several nanostructures were of different shapes and size when the potential was varied. Nanorods were prominent at the deposition potentials of −0.5 and −1.1 V, while a combination of nanostructures (nanorods, nanoplates, and nanoparticles) was predominant at −3.2 V. XRD results show that the nanostructures that were obtained consisted of tetragonal (Sn) structure with a crystallite size of about 20 nm. This process is economically viable and it can be scaled to produce various nanostructures through a careful control of deposition parameters. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessArticle Mechanical Properties of ARMCO® Iron after Large and Severe Plastic Deformation—Application Potential for Precursors to Ultrafine Grained Microstructures
Metals 2018, 8(3), 191; https://doi.org/10.3390/met8030191
Received: 22 December 2017 / Revised: 19 February 2018 / Accepted: 14 March 2018 / Published: 17 March 2018
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Abstract
Ultrafine grained (UFG) metals processed by severe plastic deformation (SPD) are well known for their outstanding mechanical properties, yet, current applications are very limited mostly due to the elaborate processing. The present work investigates the microstructures and mechanical properties of precursors to UFG
[...] Read more.
Ultrafine grained (UFG) metals processed by severe plastic deformation (SPD) are well known for their outstanding mechanical properties, yet, current applications are very limited mostly due to the elaborate processing. The present work investigates the microstructures and mechanical properties of precursors to UFG microstructures that evolve at strains below the levels required for UFG microstructures, which implies less processing effort. ARMCO® iron is subjected to a single pass of equal channel angular pressing (ECAP), cold rolling, as well as a combination of both processes and compared to strain–free samples and a UFG reference condition subjected to five ECAP passes. All conditions are characterized regarding their microstructures and mechanical properties using electron backscatter diffraction, tensile tests, and rotating bending fatigue test. The precursor states show intermediate properties in between those of the strain-free and the UFG reference condition. Compared to the processing effort, the difference in properties between precursors and UFG reference is relatively small. Especially a combination of a single ECAP pass followed by cold rolling is a good compromise in terms of processing effort and mechanical properties with an endurance limit being less than 10% lower as compared to the UFG reference condition. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessFeature PaperArticle Exothermic Reaction Kinetics in High Energy Density Al-Ni with Nanoscale Multilayers Synthesized by Cryomilling
Metals 2018, 8(2), 121; https://doi.org/10.3390/met8020121
Received: 31 December 2017 / Revised: 5 February 2018 / Accepted: 7 February 2018 / Published: 9 February 2018
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Abstract
The Al-Ni system is known as a high energy density materials (HEDM) because of its highly exothermic nature during intermetallic compound (IMC) formation. In this study, elemental Al and Ni powder were milled to explore the effect of cryomilling atmosphere on the microstructure
[...] Read more.
The Al-Ni system is known as a high energy density materials (HEDM) because of its highly exothermic nature during intermetallic compound (IMC) formation. In this study, elemental Al and Ni powder were milled to explore the effect of cryomilling atmosphere on the microstructure and exothermic behavior. Scanning electron microscope (SEM) observations show continuous structural refinement up to 8 h of cryomilling. No IMC phase was detected in the X-ray diffraction (XRD) spectrum. Differential thermal analyzer (DTA) results show two exothermic peaks for 8 h cryomilled powder as compared to that of powder milled for 1 h. The ignition temperature of prepared powder mixture also decreased due to gradual structural refinement. The activation energy was also calculated and correlated with the DTA and SEM results. The cryomilled Al-Ni powder is composed of fine Al-Ni metastable junctions which improve the reactivity at a lower exothermic reaction temperature. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessFeature PaperArticle Alkaline Metal Reagent-Assisted Synthesis of Monodisperse Iron Oxide Nanostructures
Metals 2018, 8(2), 107; https://doi.org/10.3390/met8020107
Received: 11 December 2017 / Revised: 24 January 2018 / Accepted: 30 January 2018 / Published: 5 February 2018
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Abstract
The solvothermal decomposition of iron complexes using the heat-up process enables monodisperse Fe3O4 nanoparticle synthesis. Here, we demonstrate that the high reduction potential capability of alkaline metal reagents in the reductive environment allows for pure magnetite phase formation at 200
[...] Read more.
The solvothermal decomposition of iron complexes using the heat-up process enables monodisperse Fe3O4 nanoparticle synthesis. Here, we demonstrate that the high reduction potential capability of alkaline metal reagents in the reductive environment allows for pure magnetite phase formation at 200 °C, which is lower than that of typical synthetic method and offers highly crystalline superparamagnetic and ferrimagnetic nanostructures with the ability to control uniformity including spherical and cubic morphology with narrow size distributions. Our method involved reduction of the acetylacetonate and acetate anions to aldehyde and alcohol as an oxygen resource for iron oxide nucleation in an inert condition. For confirming the developed pure surface phase of alkaline metal reagent-assisted magnetite nanoparticle, the magnetic field-dependent shifting of blocking temperature was investigated. The degree of the exchange interaction between core spins and disordered surface spins is attributed to the ratio of core spins and disordered surface spins. The decrease in disordered surface spins deviation due to an enhanced pure phase of magnetite nanoparticles exhibited the negligible shift of the blocking temperature under differently applied external field, and it demonstrated that alkaline metal reagent-induced reductive conditions enable less formation of both disordered surface spins and biphasic nanostructures. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessArticle High Hardness Nanocrystalline Invar Alloys Prepared from Fe-Ni Nanoparticles
Metals 2018, 8(1), 28; https://doi.org/10.3390/met8010028
Received: 24 November 2017 / Revised: 19 December 2017 / Accepted: 25 December 2017 / Published: 2 January 2018
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Abstract
High-density (>98% of full density) nanocrystalline invar alloys with significantly enhanced hardness (>240 in Vicker’s hardness) were prepared by sintering compacted Fe-Ni nanoparticles in hydrogen. The precursor Fe-Ni nanoparticles were synthesized by hydrogen plasma evaporation of bulk Fe61Ni39 alloys. The
[...] Read more.
High-density (>98% of full density) nanocrystalline invar alloys with significantly enhanced hardness (>240 in Vicker’s hardness) were prepared by sintering compacted Fe-Ni nanoparticles in hydrogen. The precursor Fe-Ni nanoparticles were synthesized by hydrogen plasma evaporation of bulk Fe61Ni39 alloys. The size and the productivity of the Fe-Ni nanoparticles increased with increasing hydrogen pressure. The presence of surface oxidation of the Fe-Ni nanoparticles when exposed to air was proved by the X-ray photoelectron spectra measurements. The compacted Fe-Ni nanoparticles grew rapidly at 956 °C, while the oxide impurities were removed completely by following hydrogen at 735 °C, which was found to be optimum for the synthesis of oxide-free nanocrystalline metals with fine grain size. The typical hardness of an invar alloy prepared by melting method was around 140 HV. The significantly enhanced hardness of our nanocrystalline invar alloys was potentially important in strengthening the durability of its components in instruments and in improving its machinability when machining for a component. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessFeature PaperArticle Effect of the Ultrasonic Nanocrystalline Surface Modification (UNSM) on Bulk and 3D-Printed AISI H13 Tool Steels
Metals 2017, 7(11), 510; https://doi.org/10.3390/met7110510
Received: 18 October 2017 / Revised: 14 November 2017 / Accepted: 17 November 2017 / Published: 21 November 2017
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Abstract
A comparative study of the microstructure, hardness, and tribological properties of two different AISI H13 tool steels—classified as the bulk with no heat treatment steel or the 3D-printed steel—was undertaken. Both samples were subjected to ultrasonic nanocrystalline surface modification (UNSM) to further enhance
[...] Read more.
A comparative study of the microstructure, hardness, and tribological properties of two different AISI H13 tool steels—classified as the bulk with no heat treatment steel or the 3D-printed steel—was undertaken. Both samples were subjected to ultrasonic nanocrystalline surface modification (UNSM) to further enhance their mechanical properties and improve their tribological behavior. The objective of this study was to compare the mechanical properties and tribological behavior of these tool steels since steel can exhibit a wide variety of mechanical properties depending on different manufacturing processes. The surface hardness of the samples was measured using a micro-Vickers hardness tester. The hardness of the 3D-printed AISI H13 tool steel was found to be much higher than that of the bulk one. The surface morphology of the samples was characterized by electron backscattered diffraction (EBSD) in order to analyze the grain size and number of fractions with respect to the misorientation angle. The results revealed that the grain size of the 3D-printed AISI H13 tool steel was less than 0.5 μm, whereas that of the bulk tool steel was greater than 4 μm. The number of fractions of the bulk tool steel was about 0.5 μm at a low misorientation angle, and it decreased gradually with increasing misorientation angle. The low-angle grain boundary (LAGB) and high-angle grain boundary (HAGB) of the bulk sample were about 21% and 79%, respectively, and those of the 3D-printed sample were about 8% and 92%, respectively. Moreover, the friction and wear behavior of the UNSM-treated AISI H13 tool steel specimen was better than those of the untreated one. This study demonstrated the capability of 3D-printed AISI H13 tool steel to exhibit excellent mechanical and tribological properties for industrial applications. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessArticle Peculiar Spatiotemporal Behavior of Unstable Plastic Flow in an AlMgMnScZr Alloy with Coarse and Ultrafine Grains
Metals 2017, 7(9), 325; https://doi.org/10.3390/met7090325
Received: 20 July 2017 / Revised: 14 August 2017 / Accepted: 18 August 2017 / Published: 23 August 2017
Cited by 2 | PDF Full-text (6423 KB) | HTML Full-text | XML Full-text
Abstract
The work addresses the effects of nanosize particles and grain refinement on the patterns of stress serrations and kinematics of deformation bands associated with the Portevin–Le Chatelier instability of plastic flow. Ultra-fine-grained microstructure was obtained using equal-channel angular pressing of the initial coarse-grained
[...] Read more.
The work addresses the effects of nanosize particles and grain refinement on the patterns of stress serrations and kinematics of deformation bands associated with the Portevin–Le Chatelier instability of plastic flow. Ultra-fine-grained microstructure was obtained using equal-channel angular pressing of the initial coarse-grained alloy. Tensile tests were carried out on flat specimens at strain rates in the range from 3 × 10−5 to 1.4 × 10−2 s−1. Using local extensometry techniques, it was found that the presence of nanoscale precipitates promotes quasi-continuous propagation of deformation bands in the entire strain-rate range. The grain refinement leads to a transition to relay-race propagation at high strain rates and static strain localization at low rates. The results are discussed from the viewpoint of competition between various dynamical modes of plastic deformation associated with collective dynamics of dislocations. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessArticle High-Yield One-Pot Recovery and Characterization of Nanostructured Cobalt Oxalate from Spent Lithium-Ion Batteries and Successive Re-Synthesis of LiCoO2
Metals 2017, 7(8), 303; https://doi.org/10.3390/met7080303
Received: 11 July 2017 / Revised: 27 July 2017 / Accepted: 2 August 2017 / Published: 7 August 2017
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Abstract
A complete recycling process for the cathode material of spent lithium-ion batteries is demonstrated with a simple two-step process comprised of one-pot cobalt recovery to nanostructured materials and single step synthesis of LiCoO2. For the facile and efficient recovery of cobalt,
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A complete recycling process for the cathode material of spent lithium-ion batteries is demonstrated with a simple two-step process comprised of one-pot cobalt recovery to nanostructured materials and single step synthesis of LiCoO2. For the facile and efficient recovery of cobalt, we employ malic acid as a leaching agent and oxalic acid as a precipitating agent, resulting in nanostructured cobalt oxalate. X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) analysis clearly show that cobalt species are simultaneously leached and precipitated as cobalt oxalate with a high yield of 99.28%, and this material can then be used as a reactant for the synthesis of LiCoO2 for use as a cathode material. In addition to its advantages in simplifying the process, the proposed method allows for not only enhancing the efficiency of cobalt recovery, but also enabling reaction without a reducing agent, H2O2. Through successive single-step reaction of the obtained cobalt oxalate without any purification process, LiCoO2 is also successfully synthesized. The effect of the annealing temperature during synthesis on the nanostructure and charge–discharge properties is also investigated. Half-cell tests with recycled LiCoO2 exhibit a high discharge capacity (131 mA·h·g−1) and 93% charge–discharge efficiency. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessArticle Effects of SiC Nanoparticles on the Properties of Titanium-Matrix Foams Processed by Powder Metallurgy
Metals 2017, 7(8), 296; https://doi.org/10.3390/met7080296
Received: 9 June 2017 / Revised: 17 July 2017 / Accepted: 24 July 2017 / Published: 3 August 2017
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Abstract
Metal-matrix foams are used widely for structural applications such as impact energy absorption, vibration resistance and weight reduction. In this study titanium nanocomposite foams with different porosity percentages were produced using TiH2, as foaming agent, by powder metallurgy technique. At first,
[...] Read more.
Metal-matrix foams are used widely for structural applications such as impact energy absorption, vibration resistance and weight reduction. In this study titanium nanocomposite foams with different porosity percentages were produced using TiH2, as foaming agent, by powder metallurgy technique. At first, raw materials including titanium powder and different weight percentages of SiC nanoparticles were mixed and then different amounts of TiH2 were added to the mixture. The mixture was compacted at 200 MPa. The samples were heat treated in two stages, first at 400 °C for 1 h, as a partial sintering, and then at 1050 °C for 2 h, as foaming treatment. Mechanical and structural properties such as compressive strength, energy absorption, porosity percentage and relative density of samples were measured and compared together. Thermo gravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed on foaming agent and samples. The results showed uniform distribution of SiC nanoparticles in titanium matrix and also homogenous pore structure. It was concluded that with increasing SiC weight percent, relative density is increased to 0.43 in the sample with 1.5 wt % SiC. Besides, the measured compressive strength of samples was in the range of 14.4–32.3 MPa. Moreover, it was concluded that the energy absorption of samples increases with increasing SiC nano particles up to 33.09 MJ/m3. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessArticle Enhanced Surface Precipitates on Ultrafine-Grained Titanium in Physiological Solution
Metals 2017, 7(7), 245; https://doi.org/10.3390/met7070245
Received: 17 May 2017 / Revised: 15 June 2017 / Accepted: 27 June 2017 / Published: 1 July 2017
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Abstract
Enhanced cell adherence to the surface of nanocrystallized commercially pure titanium (CP–Ti) was observed by several authors. However, the understanding of the surface modification of Ti in a physiological solution due to nanocrystallized grain size has not been reached. In this work, equal
[...] Read more.
Enhanced cell adherence to the surface of nanocrystallized commercially pure titanium (CP–Ti) was observed by several authors. However, the understanding of the surface modification of Ti in a physiological solution due to nanocrystallized grain size has not been reached. In this work, equal channel angular pressing (ECAP) was applied to manufacturing ultrafine grained CP–Ti. Martensite and Widmanstatten microstructures were also obtained for comparison. The CP–Ti pieces with different microstructures were subjected to soaking tests in a simulated body fluid. Electrochemical impedance spectroscopy (EIS) measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM), energy dispersive spectrometer (EDS) were used to characterize the surfaces. The results show the surface precipitates mainly contain Ti, O, Ca and P. The quantity of precipitates on ECAPed CP–Ti is the largest among different specimens corresponded to the observation of the thickest layer formation on ECAPed CP–Ti found by EIS. EDS results show more CaPO and less Ti are included on ECAPed Ti comparing to the deposits on other two types of specimens. Smaller numbers of precipitates and denser film are produced on the surface of the water-quenched CP–Ti. The regeneration kinetics of the CaP precipitates evaluated by Gibbs free energy is introduced to interpret the precipitating behaviors on different CP–Ti specimens. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessArticle Synthesis and Characterization of Nano-Particles of Niobium Pentoxide with Orthorhombic Symmetry
Metals 2017, 7(4), 142; https://doi.org/10.3390/met7040142
Received: 27 March 2017 / Revised: 10 April 2017 / Accepted: 13 April 2017 / Published: 19 April 2017
Cited by 3 | PDF Full-text (831 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this work, a set of nanoparticles of Nb2O5 nanoparticles were grown by both the Pechini and the sol-gel methods. The amorphous materials were calcined at 650 #xB0;C or at 750 °C. X-ray diffraction, scanning electron microscopy, luminescence and Raman
[...] Read more.
In this work, a set of nanoparticles of Nb2O5 nanoparticles were grown by both the Pechini and the sol-gel methods. The amorphous materials were calcined at 650 #xB0;C or at 750 °C. X-ray diffraction, scanning electron microscopy, luminescence and Raman spectroscopy were used in order to characterize the materials. From the study, it is possible to state that the method of production of nanoparticles, beyond the temperature of synthesis, has a great influence on whether the phase produced is hexagonal or orthorhombic. Additionally, compared to de Sol-gel method, the Pechini method produced samples with smaller particle sizes. The photoluminescence spectra of niobium pentoxide nanostructure materials show that the emission peaks are positioned between 334 to 809 nm and there is a change of intensity which varies depending on the synthesis route used. High pressure Raman spectra at room temperature were obtained from two samples grown by the sol-gel method. Up to 6 GPa, where it is possible to observe the Raman bands, no modification other than the increase of disorder was observed, and this can be associated with a change of phase. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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